Mucking machine



Feb 12, 1%?

W. L. CRYDEFRMAN MUCKING MACHINE 4 Shets-Sheet 1 Filed 001:. 20, 1955 Inventor 146mm? 1. LRYDZKMAA/ Att 'ys W. L. CRYDERMAN MUCKING MACHINE ZJSLMQ 4 Sheets-Sheet 2 'lrwe ntor Attys Feh @957 w. L, CRYDERMAN' 2,783,2 3

MUCKING MACHINE Filed 001:. 20, 1955 4 Sheets-Sheet 5 Mb, 12, 1957 w. L. CRYDERMAN 2,7 9%

MUCKING MACHINE Filed Oct. 20, 1955 4 Sneaks-Sheet BOOM DU 7' EXHAUST sr/cx FORWARD BUCKET OPEN STICK RIGHT EXHAUST BUCKET CLOSED si'lck LEFT inventor Mum 1. wrap/1,4

United States Patent MUCKING MACHINE Warner L. Cryderman, Skead, Ontario, Canada, assignor to Shaft Machines Limited, Toronto, Ontario, Canada Application October 20, 1955, Serial No. 541,690

10 Claims. (Cl. 214-657) This invention relates to a mucking machine for loading material at the bottom of a mine shaft caisson or the like.

It is an object of the invention to provide a mucking machine of the type having a cage from which a tel scoping boorn with a clam on a free end thereof is suspended. The cage is of an improved type which permits of a reduction in the width of the machine and which makes the machine more suitable for mucking in an inclined as Well as vertical shaft.

it is a further object of the invention to provide an improved means for telescoping the telescoping boom operating the clam, and a better arrangement for swinging the boom to the desired position.

Generally speaking, a mucking machine according to my invention has a cage from which is suspended a telescoping boom. The boom is suspended in a gimbal type of suspension, and has a clam on its free end. Means are provided for telescoping the boom, for moving the boom in any direction within its suspension and for operating the clam on the free end thereof, whereby muck can be lifted from the bottom of the shaft and deposited in conveying means for removal. The invention will be clearly understood after reference to the following detailed specification read in conjunction with the drawings.

In the drawings:

Figure 1 is a perspective view of a mucking machine according to the invention illustrating the manner in which the telescoping boom is supended from the cage;

Figure 2 is a cross-sectional View of the boom;

Figure 3 is a view along the line 3-3 of Figure 2;

Figure 4 is a view of valve arrangement for controlling the operation of the boom and buckets;

Figure 5 illustrates how the control valves are connected;

Figure 6 is a plan view of valve ports;

Figure 6a is a diagram showing control direction; and

Figures 7, 8, 9 and 10 are views schematically showing the operation of the valves for the telescoping of the boom and for the operation of the clam.

Referring to the drawings, the numeral 10 generally indicates a mucking machine. It has a cage generally indicated by the numeral 11 from which the operator controls the operation of the mucker. Channels 12 on the side of cage 11 are adapted to engage with guides in one compartment of a vertical shaft in which the machine is operated. Numerals 13 and 13a indicate the control levers for the mucking machine;

A telescoping boom generally indicated by the numeral 14 and to be more fully described later, is suspended from the cage by means of a gimbal type suspension. The suspension illustrated comprises a yoke 15, mounted to swing about a first axis thereof 'by means of the pins 16 which are retained by brackets 17 and 18 on opposite sides of the cage 11. The boom 14 is swingably mounted in the yoke to swing about a second axis between the sides of the yoke 15 by. means of mounting 2,781,146 Patented Feb. 12, 1957 pins 19, only one of which is visible in Figure 1. It will be noted that the first axis of the yoke 15 referred to is substantially at right angles to the second axis of the yoke referred to, whereby the boom 14 can be moved in any direction within its suspension.

Means are provided for moving the boom 14 in any direction within its suspension, which in the embodiments shown include the cylinders and co-operating pistons generally indicated by the numerals 20, 21 and 22 and 23.

The cylinders 22 and 23 are adapted to swing the boom about the first swing aXis of the yoke 15, that is about the pins 16 and 17 and are universally jointed at both ends.

The cylinders 20 and 21 are adapted to swing the boom 14 about the second swing axis of the yoke that is about the pins 19, and are pivotally attached to the yoke itself.

Each of the cylinder and piston arrangements 20 to 23 inclusive are similar and each comprises a cylinder having a double acting iston therein with a piston rod which extends from and retracts into the cylinder according to the movement of the piston. The piston is operated by compressed air or a hydraulic fluid that is controllably forced into either end of the cylinder to achieve the action in both directions. The air or fluid connection to the two ends of the cylinder of the piston and cylinder 23 have been indicated by the numerals 23a and 23b. The operation of double acting piston and cylinder arrangements is Well known and it is thought that from the illustration given in Figure 1 they are sufliciently explained to persons skilled in the art and it is not my intention to burden this application with further details of their construction or operation.

It will be noted that the cylinders and pistons 22 and 23 universally connect with the boom as at 24, and with the cage 11 as at 25. The cylinder and pistons 20 and 21 on the other hand are not universally connected at either of their ends, but merely pivotally connected as at 25 and 27. i am able to avoid the use of a universal connection for the cylinders 20 and 21 by reason of the gimbal mounting for the boom.

The clam on the free end of the telescoping boom 14, comprises two co-operating buckets 32 and 33 which are operated about their pivotal mounting 34 by means of the double acting cylinder and pistons 35 and 36. Pistons 35 and 36 are pivotally mounted at each of their ends as at 37 and 38 and are operated to move their respective clam buckets to closed and open positions as desired in a well known manner, which it is not thought necessary to explain in this application.

The means for telescoping the boom is illustrated in detail in Figures 2 and 3 of the drawings.

The boom generally indicated by the numeral 14 has two sections, a first section 39 suspended Within the yoke 15 as described above and a second section 46 which telescopes therewithin. Numerals 41 indicate bearings engaged by the mounting pins 19. The second section 49 has a smaller diameter than the first section 39 and defines an annular space between the two as illustrated in the sectional views of the drawings. Numeral 42 indicates a bronze bushing which acts as a bearing for the telescoping movement between the two. It is carried by the second telescoping section 40. Numeral 43 indicates a similar bronze bushing carried by the first and stationary section 35.

The telescoping movement of the telescoping section 40 of the boom is controlled by the fixed double acting piston head 44, the surface 45 of which together with the plate 46 of the telescoping boom section 40 defines a first chamber, and the surface 47 of which together with the closed end 48 of the telescoping boom section:

40 forms a second chamber.

Means are provided for admitting and exiting fluid to each of these two chambers for the purpose of moving the telescoping section 40 inwardly and outwardly of the rigid section of the boom 39.

I have operated a telescoping boom as described by means of air pressure and'in this description it will be assumed that air is being used. However, it will be apparent that one could operate" the system successfully with a liquid such as oil instead of air.

Air in operation is admitted to the first chamber by means of the pipe 50, which at its lower end communi cates with the said chamber.

As air is admitted to the first chamber, it builds up a pressure and forces the end 46 thereof away from the rigid surface 45 of the piston 44 telescope the boom section 46 outwardly of the rigid boom section 39. It will be apparent that as the teiescoping action takes place, it will be necessary to evacuate air from the second chamber. 7 The escape of this air takes place through the openings 51 in the tube 52 through the an nular space 53 between tube 52 and 59 through chamber and out opening 55, to a suitable exhaust pipe.

Tube 52 is rigidly mounted with respect to the rigid sec;ion 39 of the boom 14 and a packing gland generaily indicated by the numeral 56 is provided to seal the opening in the end 48 of the telescoping section 4%} of theboorn 14. Packing gland 56 has an air sealing 1 packing generally indicated by the numeral 57 and bronze bushings 53 and 59.

Means are provided for cushioning the telescoping section 4% of the boom 14 as it approaches the full outward extent of its travel. In this connection the bushing 58 mounted within it and it is upon the upper end of the is adapted to slide over the openings 5 of the tube 52 V to substantially close off the escape of air therethrough just prior to when the section reaches the full extent of its travel. This causes a build-up of air pressure in the second chamber and avoids a stopping of an outward travel of the section 49 by the abrupt mechanical locking of tr e two sections of the boom.

When it is desired to cause the boom section 40 to retract, air under pressure is forced into the opening through the chamber 54 downwardly through the annular space between the pipe 50 and the pipe 52 and outwardly through a check valve 60 into the second chamber. This causes a build-up of pressure in this chamber and causes the boom section 40 to move inwardly. At the same time air is evacuated from the first chamber referred to through the pipe 59 which has been disconnected from the sup 'ply which previously caused the build-up of pressure therein and is now connected to exhaust. Once the bushing 56 has been caused to uncover the opening 51 as the section moves inwardly, the air will enter into the second chamber through the opening 51.

in order to cushion the upward travel of the section as the section 40 approaches the limit of its inward travel a pin, generally indicated by the numeral 61, is provided on the plate 46 and is adapted to enter into the lower extremity of tube 50 to slow up'the escape of air therethrough and cause a build-up of air pressure in the second ch amber.

I should perhaps refer now specifically to the manner in which the piston 44 is mounted. It is carried by the tubing 52, which in turn is rigidly mounted to the top 63 of the rigid section 3? of the boom 14. Tube 52 has its upper endturned down to receive the steel ring 64, and a nut 65 is threaded over the free turned down end of tube 52 to rigidly mount the latter with respect to the top 63. Nut 65 is formed with the chamber 54 previously mentioned and a suitable packing is provided as at 66 to prevent undue leakage from the latter where the tube 5'9 extends therefrom. Tube 56 passes in spaced relation within tube 52 to define the annular passage 53 previousiy mentioned and is threaded at its free end to receive the'securing nuts 52a.

The lower portion of the sliding section 4%) of the boom is internally reinforced by a second tube 67 secon'dt'ube that the plate 46 is mounted.

In use oil often collects in the lower chamber and a drain 68 normally closed by means of a plug is provided, through which the oil can be drained off.

The clam assembly is carried on the sleeve 70 which, as illustrated in Figure 2, fits over the free end of the projecting or telescoping section {10 of the boom. The section 40 of the boom has a flange 71 to which the sleeve 70 is bolted around its circumference as indicated at 71a; A gasket 72 is interposed between the ring 72a and the end of the telescoping section 40 of the boom to absorb shock iii-operation;

In Figure 4 1 illustrate the control levers and control valves which form part of the control means for telescoping the boom, moving the boom within its mounting, and operating the clam.

As indicated above the telescoping boom 14 and the cylinders 20, 21, 22, 23, 35 and 36 are all air operated.

They are each double acting and the supply of fluid;

77 controls the supplyo'f air to the cylinders 20 and 21;

Valves 74, 75, 76' and 77 are each four way valves.

They are arranged in pairs, the valves 74, 75 comprising one pair, and the valves 76 and 77 comprising the other pair, and the supply of operating fluid to the first pair is through the conduit 78; The supply of fluid to i the second pair is through the conduit 79.

In Figure 6 the four openings of each of the valves are illustrated. The input of air is to the openings 80,

a $1, 82 and 83 for the valves 74, 75, 76 and 77 respectiv'ely. The openings 84,- 85, S6, and 87- 'of the valves 74', 75, 76 and 77 respectively all connect to an exhaust'. 1

Each of the valves has four openings and in each case one of them connects with one chamber of the cylinder which it controls and another connects with the other chamber thereof. The valve itself is adapted to' controllably connect the two chambers of the cylinders with an air supply and an' air-exhaust line whereby to operate the'piston within the cylinder inwardly and outwardly.

I willillustratethis manner of connection as it applies to the valve 74 which controls the telescoping boom.

The opening 88 of valve 74 is connected to the passage 55 by means of asuitable conduit and the opening 89 of valve 74 connects with the passage 59 by means of a suitable conduit. The valve has a control arm 92 which is rockably mounted on the body thereof to swing about a first axis that coincides with the longitudinal axis of duit 50 or the conduit- 55; In the former case the exhaust being connected to the conduit 55 and in the latter case the exhaustbeing connected to the opening 56.

The valve 75 is similar to the valve 74 and is adapted to be operated by the common lever 13a. Itis, however, arranged with its firstaxis which coincides with rocking bar 97a at right anglesto the said first axis of the controlarm 92 and was its second, axis which coincides with thelongitu'dinal-axis or" bar 971; at right angles to the said second axis so that the yoke 96 can swing about the second axis 971). Link 95 is welded to yoke 96 at one end and slidably connects with handle 13a through ring 95a as illustrated.

It will be apparent that when lever 13a is moved to the right or to the left as viewed in Figure rocker arm 92 will be moved about its first axis that is about bar 92:: but no movement of the rocker arm 97 will result, as the yoke 95 swings about the second axis which coincides with bar 97b thereof. Conversely it will be apparent that when the lever 13a is moved to the right or left as viewed in Figure 4 no movement of the rocker control arm 97 will result. Four way valves of the poppet type having a rocker control are well known in the art and are in present use so that a detailed description of them is not thought necessary.

The two positions of operation of valve 74 as controlled by lever 13:: have been graphically illustrated in Figures 7 and 8. It Will be apparent that when the valve is operated to the position illustrated in Figure 7 that the boom will move outwardly or extend itself, and when the valve is actuated to the position illustrated in Figure 8 that the boom will move inwardly. The control lever 13:: is preferably arranged so that when it is moved towards the operatonthe valve position of Figure 8 results and the boom moves inwardly, and when the lever 13 is moved away from the operator, the valve position of Figure 7 results, and the boom moves outwardly.

The buckets on the free end of the boom are controlled in operation by the valve 75. They are similarly operated so that the air supply connection for each one is controlled by a single valve. In the case of the buckets the valve control arm 97 is controlled by means of the link 95 which extends from the lever 13a to the yoke 96 as described above.

It will be apparent that when the lever 13a is swung to the right or left as viewed in Figure 5 that the rocking valve arm 92 will be actuated, and that the rocking valve control arm 97 will be unaffected as the yoke 96 rocks about the second axis of the control arm. As indicated above the extreme right and extreme left position of the lever 13a as viewed in Figure 4a are represented by Figures 7 and 8, and control the movement in and out of the telescoping boom.

When the lever 13a is moved to the right or the left as viewed in Figure 5 the control arm 92 of valve 74 is unaffected as the lever 13a rocks about the second axis 92b of control member 92. The control arm 97 however of the valve 74 is rocked to control the supply of air to the bottom end of the cylinders 35 and 36 and to exhaust the top end of the same cylinders when the stick is to the left as viewed in Figure 5, and to supply air to the top of the cylinders 35 and 36 and exhaust the bottoms thereof when the stick is moved to the right as viewed in Figure 5. The right and left control positions of the valve 75 have been illustrated in Figures 8 and 9 of the drawings.

With the control valves 74 and 75 arranged as described, that is with their rockable control arms having their rocking axes at 90 to each other and each having a yoke swingable thereabout connected by means of the control lever 13:: and line 95 as illustrated, the telescoping of the boom and operation of the clam can be simply controlled. The operator, who stands behind the controls, by pushing the control lever 13a away from him causes the boom to move outwardly. If the lever 13a is towards his right the bucket of the clam will be open and, by moving the lever towards his left, he operates valve 75 to cause the bucket to close. muck. By pulling the lever towards him with the lever in its left handed position, the boom retracts. When it is retracted sufficiently, he can cause the bucket to open to dump the load by moving the lever to his right.

Thus by moving the lever with a counter-clockwise mo- This fills the clam with l 6 tion as indicated by the arrows that extend from A' to E to C to D in Figure 6a he causes the boom to travel outwardly to close and take up muck, to retract and then to open to dump muck.

The valve 76 controls the pair of cylinders 22 and 23 and the valve 77 controls the cylinders 20 and 21. The valves are similarly operated and controlled by the control lever 13 to cause the boom to swing in any desired position within its mounting. It should perhaps be mentioned that the cylinders 26 and 21 are connected so that one is moving outwardly as the other is moving inwardly because they are on opposite sides of the boom. It is thought that a person skilled in the art would have no trouble in connecting the cylinders from the detailed explanation given in connection with the boom and bucket cylinders. The essential feature about the manner of connecting is a valve having a control element that. rocks, and a yoke that rocks substantially about the swing axis thereof with a handle connected to it so that the handle can be moved to operate the rocking control element and also moved in a direction at right angles thereto without affecting the particular valve but connected to a similar valve to operate it.

I claim:

1. In a mucking machine a cage, a telescoping boom, a clam on the free end of said boom, means for telescoping said boom, a gimbal type suspension for suspending said boom from said cage, means for moving said boom in any direction within its suspension, means for operating said clam, said gimbal type suspension comprising a yoke, means for mounting said yoke on said cage to swing about a first swing axis of said yoke, means for mounting said boom on said yoke to swing about a second swing axis of said yoke, said first axis being at right angles to said second axis, said means for moving said boom comprising a first cylinder and piston means connecting with said cage and with said boom and adapted to swing said boom about said first swing axis, and a second cylinder and piston means connecting with said yoke and with said boom and adapted to swing said boom about said second swing axis said first cylinder and piston means being universally connected whereby to swing said boom about said first swing axis for all positions of swing of said boom about said second swing axis.

2. A mucking machine as claimed in claim 1 in which said telescoping boom has two sections, the first section being suspended from said cage as aforesaid and the second section being adapted to telescope with respect thereto, said means for telescoping said boom including a double acting piston head rigidly mounted with respect to said first section of said boom and within said second section of said boom, the ends of said second section each being sealed whereby to form a first and a second chamber, one on each side of said piston, means for admitting and exiting fluid to said two chambers of said boom on each side of said section whereby said second section of said boom can be caused to move in either direction with respect to said piston and said first section of said boom.

3. A mucking machine as claimed in claim 1 in which said telescoping boom has two sections, the first section being suspended from said cage as aforesaid and the second section being adapted to telescope with respect thereto, said means for telescoping said boom including a double acting piston head rigidly mounted with respect to said first section of said boom and within said second section of said boom, the ends of said second section each a 7 said boom has two sections, one telescopingwithin the other and in which said means-for telescoping said-boom includesa valve means, a piston adapted to'co-operate with one of said boom sections to form two chambers therein, said valve means being adapted to control flow of an operating fluid to .either chamber of said boom section with said piston and to exhaust fluid from the other chamber thereof, and in which said means for operating said clam includes valve means, and a double acting co-operating piston-cylinder, said cylinder having two chambers one on each side of said piston, said valve means being adapted to control flow of an operating fluid to either chamber of said cylinder and to'exhaust fluid from the other one, and in which said valve means of said means for telescoping said boom and said valve means of said means for operating said clam have a common control lever.

5. In a mucking machine a cage, a telescoping boom, a clam on the free end of said boom, means for telescoping said boom, a gimbal type suspension for suspending said boom from said cage, means for moving said boom in any direction within its suspension, means for operating said clam, said gimbal type suspension comprising a yoke, means for mounting said yoke Unsaid cage to swing about a first swing axis of said yoke, means for mounting said boom on said yoke to swing about a second swing axis of said yoke, said first axis being at right angles to said second axis, said'means for moving said boom comprising a first cylinder and piston means connecting withsaid cage and with said boom and adapted to swing said boom about said first swing taxis, and a second cylinder and piston means connecting with said yoke and with said boom and adapted to swing said boom about said second swing axis, said first cylinder and piston means being universally connected whereby to swing said'boom about said first swing axis for all positions of. swing of said' boom about said second swing axis, said second cylinder and piston means extending from one side only of said boom.

6. In a mucking machine a cage, a telescoping boom, a clam on the free end of said boom, means-for telescoping said boom, a gimbal type suspension for suspending said boom from said cage, means for moving said boom in any direction within its suspension, means for operating said clam, said boom having two sections, one section telescoping within the other, said means for telescop- .ing said boom including a valve means, a piston adapted to cooperate with one of said boom sections to form'two chambers therein, said valve means being adapted to conboom section with said piston and to exhaust fluid from the other chamber thereof, said means for operating said clam including valve means, and a double acting cooperating piston-cylinder, said cylinder having two chambers one on each side of said piston, said valve means being adapted to control flow of an operating fluid to eith r chamber of said cylinder and torexhaust fluid from the other one and in which said valve means of said means for telescoping said boom and said valve means of said means for operating said clam'have a common control lever, said control element including a lever operable in two directions, said lever being adapted to control one said valve means as aforesaid when actuated in one direction and to control the other of said valve means as aforesaid when actuated in the other direction.

7. in a mucking machine a cage, a telescoping boom, ciam on the free end of said boom, means for telescopsaid boom, a gimbal type suspensionv for suspending boom from said cage, meansfor moving said boom 11 any direction within its-suspension, means for operating said clam, said boom having two sections, one section telescoping within the other, said means for telescoping said boom rein-ding a valve means, a piston adapted to co-operate with one of said boom. sections to form two chambers therein, said valve means being adapted to control how of an operating fluid to either chamber of said boom section with saidpiston'and to exhaust fluid from the other chamber thereof, saidrneansfor operating said clam including valve means, and a-double acting co-opcrating piston-cylinder, said cylinder having'twochamhers one on each side'of said piston, said valve means beingadapted to control flow of an operating fluidto either chamber of said cylinder and to exhaust fluid from the other one and in which said valve means of said means for telescoping said boom 'andsaid valve'means ofsaid means for operating saidclam have a common control lever, said control element including a lever openable in two directions, said lever being adapted to control one of said valve means as aforesaid when actuated in one direction and to control the other of said valve means as aforesaid when actuated inthe other direction, said lever being adaptedto'freely rock with respect to said control arm onwhich it is mounted.

8. In a mucking machine a cage, a telescoping boom, clam on the free end of said boom, means for'telescoping said boom, a gimbal type suspension for suspending said boom from saidcage, means for moving said boom in any direction within its suspension, means for operating said clam, said boom having two-sections, one sectiontelescoping with the other, said-means for'telescoping said boom including a valve means, a piston adapted to co-operate with one of said boom sections to form, two chambers therein, said valve means being double acting co-operating' piston-cylinder, said cylinderhaving two chambers one on. each side of said piston,

said valve means being adapted to control flow of an operating fluidto either chamber of said cylinder and to exhaust fluid from the other one and in which said valve means of said'means for telescoping said boom and said valve means of said means for operatingsaid clam have a common control lever, said control element including a' lever operable in two directions, said lever being adapted to control one of said valve means as aforesaid When. actuated in one direction and to control the other of said valve means as aforesaid when actuated in the other direction, said valve means. being similar and each having a control arm, each of said control arms having afirst axis and a second axis at right angles to the first axis, each of said control arms being mounted on its respective valve means to swing about the first axis thereof, the first axis of one of said valve means being at right angles to the first axis of the other of said valve. means, said lever being adapted to swing about the second axis of the first one of said valve means, a link, one end of. said link being connected to the secondaxis of said second valve to swing thereabout, the other end of said link being connected to said lever but adapted to slide longitudinally thereof whereby said lever'is capable of rocking the control arm of either of said two valves separately.

9; a mucking machine a cage, a telescoping boom, a clam on the free end of said boom, means for telescoping said boom, a gimbal type suspension for suspending 7 said boom from said cage, means for moving said boom in any direction within its suspension, means for operating said clam,said gimbal type suspension comprising a yoke, means for mountingsaid yoke on said cage to swing i about a first swing axisot said yoke, means for mounting said boomon said yoke to swing about a second swing axis of said yoke, said first axis being at ri'ghtangles to said second axis, said means for moving said boom comprising a first cylinder and piston means connecting second swing axis, said first cylinder and piston means being universally connected whereby to swing said boom about said first swing axis for all positions of swing of said boom about said second swing axis, said means for moving said boom further including a first valve means connected to said first cylinder and piston means to control the flow of operating fluid thereto in use and second valve means connected to said second cylinder and piston means to control the flow of operating fluid thereto in use, said first valve means and said second valve means having a common control element, said control element including a lever operable in two directions, said lever being adapted to control said first cylinder and piston means as aforesaid when actuated in one direction and to control said second cylinder and piston means as aforesaid when actuated in the other direction.

10. A mucking machine as claimed in claim 6 in which said means for moving said boom in any direction Within its suspension includes a first cylinder and piston means connecting with said cage and with said boom and adapted to swing said boom about said first swing axis, and a second cylinder and piston means connecting with said yoke and with said boom and adapted to swing said boom about said second swing axis, said first cylinder and piston means being universally connected whereby to swing said boom about said first swing axis for all positions of swing of said boom about said second swing axis, said means for moving said boom further including first valve means connected to said first cylinder and piston means to control the flow of operating fiuid thereto in use and second valve means connected to said second cylinder piston means to control the flow of operating fluid thereto in use, said first valve means and said second valve means having a common control element, said control element including a lever operable in two directions, said lever being adapted to control said first cylinder and piston means as aforesaid when actuated in one direction and to control said second cylinder and piston means as aforesaid when actuated in the other direction.

References Cited in the file of this patent UNITED STATES PATENTS 1,307,009 Joy June 17, 1919 2,456,320 Repke Dec. 14, 1948 2,606,679 Cryderman Aug. 12, 1952 2,639,048 Glashaw May 19, 1953 2,643,515 Harsch June 30, 1953 2,731,163 Wills et al Jan. 17, 1956 

